In a secondary battery employing a lithium anode it is desirable to employ an electrolyte system which provides high cycling efficiency, good conductivity, and reasonable cost. The number of times a lithium battery can be recharged, and the efficiency of each recharging are the measures of cycling efficiency. Cycling efficiency of the Li electrode is primarily a function of the ability of the electrolyte solvent to withstand reduction by lithium, which is a powerful reducing agent. When reduction occurs, reaction products form on the surface of the lithium electrode preventing subsequent smooth replating during the recharge cycle. This results in dendritic growth and consequently poor lithium morphology.
Various ethers have been used in combination with lithium salts and rechargeable electrochemical cells. U.S. Pat. No. 4,060,674 describes "electrolyte compositions for reversible alkali metals cells, e.g. lithium batteries . . . which consist of . . . ethers . . . and . . . alkali metal salts." Among the types of ethers mentioned is "orthoesters." U.S. Pat. No. 3,578,500 describes "primary or secondary electrochemical cells" having "preferred active anode materials such as lithium and sodium." A list of solvents includes 2,2-dimethoxypropane and trimethylorthoformate, and a list of salts includes "lithium hexofluoroarsenates." Other combinations include dioxolane/LiClO.sub.4, U.S. Pat. No. 4,086,403; tetrahydrofuran (THF)/LiAsF.sub.6, U.S. Pat. No. 4,228,227; 2-methyltetrahydrofuran (2MeTHF)/LiAsF.sub.6, U.S. Pat. No. 4,118,550; and diethyl ether (DEE) mixtures with cosolvents/LiAsF.sub.6, U.S. Pat. No. 4,252,876.